Among conventional boots of this kind is a boot that includes a freely extendable and contractible bellows part, a large-diameter annular mounting part formed at one end in the axial direction of this bellows part, and a small-diameter annular mounting part formed at the other end in the axial direction, and is molded by blowing material such as thermoplastic elastomer.
In the boot of this kind, the large-diameter side mounting part is fixedly fastened by one clamp to the outer peripheral surface of an end portion of one shaft of two members that can move relatively to each other and the small-diameter side mounting part is fixedly fastened by another clamp to the outer peripheral surface of the other shaft.
With this, the bellows part can be flexibly deformed with the relative movement of the two members to prevent foreign matters from entering a movable mechanism between the two members from the outside and to prevent lubricating grease or the like filled in the movable mechanism from leaking to the outside.
As for the boot described above, there has been known a boot that is used for protecting a constant-velocity joint used for transmitting a driving force in an automobile. Further, there is a case where the outer peripheral shape of the fixed part of a joint cup having the boot mounted thereon is not cylindrical but may be formed in the shape of a deformed cylinder that has three curved depressions, so-called tripod. In this case, in the conventional boot, the inner periphery of the fixing part of the boot is formed in the shape of a tripod according to the shape of the outer periphery of the fixing part of the cup and the outer periphery of the fixing part of the boot is formed in a cylindrical shape. The outer periphery of the fixing part of the boot is fastened by a band, whereby the boot is fixed to the cup.
Further, a construction has been proposed in which, when both of the boot and the cup are made of hard materials, an adaptor member made of rubber or elastic plastic that is soft and can be easily deformed is interposed between the boot and the cup so as to eliminate the gap between the respective members at the fixing part (see for example, U.S. Pat. No. 6,402,999). To be specific, as shown in FIG. 10, to mount a boot 101 on a case (not shown) formed in the shape of a tripod, an adaptor member 110 having a circular outer peripheral surface 111 and an inner peripheral surface 113 having convex portions 112 corresponding to the shape of a tripod of the outer periphery of the fixing part of the case is made separately from the boot 101 main body. Then, the adaptor 110 is fitted in the boot 101 and is further mounted on the case to cover and protect the movable mechanism of a constant-velocity joint.
Further, a construction has been proposed in which an annular rubber bush 130 is mounted on the opening end edge 122 of a hollow cylindrical boot body 128 made of synthetic resin as a dust preventing boot of constant-velocity joint (see, for example, Japanese published unexamined utility model application No. 60-64362). The rubber bush 130 is formed in the shape of a letter C in section and the opening end edge 122 is closely fitted in the center depressed groove 132. The rubber bush 130 is pressed onto the outer peripheral surface 116 of the case by a fastening band 134 mounted on the outer peripheral surface of the rubber bush 130. Here, FIG. 11A is a sectional view of a dust preventing boot 126 and FIG. 11B is an enlarged sectional view of a portion enclosed by a dotted line in FIG. 11A.